Five days had already passed at that point since the mass abduction on April 14. The militant Islamist group Boko Haram later claimed responsibility for the kidnappings. Boko Haram means "Western Education is a Sin," and in a video message, a leader of the group threatened to sell the schoolgirls and force them to marry.

Protesters Demand Action on Kidnapped Nigerian Girls

"I believe that we've been desensitized to what goes on in Africa," Mosley said. "To think that, in 2014, schoolgirls can be kidnapped from their schools is barbaric."

Mosley, a director of commercials and documentaries, said that she decided to transform her initial feeling of powerlessness into action. She thought about getting on a plane to Chibok, Nigeria, where the students were kidnapped, but her 11-year-old daughter begged her not to go out of concern for her mother's safety.

"She asked me to try to think of a way to help from here," Mosley said. "I decided what I would do is that I would put out a call on social media."

Mosley knew that some people in Nigeria were repeating the mantra, "Bring back our girls. The hashtag was gaining traction on Twitter. Its first registered user, according to Topsy social media analysis, was Ibrahim M. Abdullahi. In Abdullahi’s April 23 tweet, he echoed a phrase that he had heard Oby Ezekwesili, a former World Bank Vice President, say in a speech.

On April 25, Mosley decided to start tweeting, “Bring back our girls,” as well.

"I started shouting it on social media hoping that people would listen and they would shout it back,” she said, “and so first I started shouting to all my friends. Then I started shouting it to Barack Obama.”

The chorus would continue to grow. The phrase has now been used on Twitter more than 800,000 times, including by celebrities Kerry Washington and Chris Brown. On Sunday, Hillary Clinton tweeted, "Access to education is a basic right & an unconscionable reason to target innocent girls. We must stand up to terrorism. #BringBackOurGirls."

“I jumped up and I cheered," Mosley said, describing her reaction to Clinton’s tweet. "I realize that it seems like a hashtag is a trivial thing. But actually it's not. It's an SOS to the world."

Mosley created a Facebook page to amalgamate information about the situation and give people suggestions about ways that they can take action. The page now has 43,000 likes.

"I am living this 24/7," she said. "This has consumed my life and I believe it will until the girls are rescued."

Last night, Mosley attended a protest in Los Angeles, where about a hundred people gathered and chanted, "Bring back our girls." She said that some of the people who contact her through Facebook have been asking her for permission to organize protests.

"I say this is for you to give yourself permission to do," Mosley said. "Every one of us should be marching and protesting."

Editor’s note: This story has been updated to reflect that #BringBackOurGirls appeared on Twitter prior to Ramaa Mosley’s first tweet and with additional information about the evolution of that hashtag.